Mar 5th 2025
Why Nissan’s 35 year-old engine is still relevant - all about the SR20DET
We’re taking a deep dive into Nissan’s SR20DET engine. Despite being 35 years old, these engines have stood the test of time and are still relevant to this day.
We’re going to discuss the history, what makes them so good, how they stack up against similar motors, and finally, the proper way to build one in 2025.
Quick links
- A history of the SR20DET
- Why the SR20 is legendary
- Where the SR does/doesn't shine
- SR20DET versions
- The SR's Achilles heel
- Building an SR20DET
A history of the SR20DET
A good place to start is with the name. If you’re not familiar with Nissan nomenclature, the name can be broken down to:
SR = the engine family, it doesn’t mean anything special - just a name
20 = the size of the engine is 2.0 liters
D = dual overhead camshaft, equal to ‘DOHC’ on Hondas
E = electronic fuel injection
T = turbocharger (the most important part)
You probably know them as the engines found in the S13, S14, and S15. This is the version we’re talking about today: the RWD, turbo SR20. There’s also a NA version, the SR20DE, found in lower trim S-chassis. These are still decent engines, just missing some goodies.
Starting in 1991, if you live anywhere outside of North America, your 180sx, 200sx, or Silvia would have come with an SR, whereas in North America our 240s came with a truck engine.
The SR was a replacement for the CA18DET. If you’re unfamiliar with the CA, it’s basically a shortened RB engine. It uses a cast iron block and aluminum head. While they aren’t terrible engines, they struggle to compete with the all-aluminum SR20. And no, the higher output doesn’t come from the extra .2 liters of displacement. SRs make power because of a better flowing head, netting a 50HP gain over its predecessor.
You should also know that there are FWD versions of the SR. These were actually in use a few years before the S13 and carried on a few years after the last S15. Some have different displacements. A 1.6 liter SR16VE can be found in the Pulsar GTI-R and a 1.8 SR18DE in the Primera. In the States, we got a 2-liter FWD in the Sentra. Unfortunately, not a lot of parts are interchangeable between FWD and RWD applications - or at least not the parts you need.
What makes the SR a legendary engine?
The chassis it came in
A legendary car needs a legendary engine, and vice versa. Think Supras, EVOs, etc. The SR20 is another prime example being installed in the S-chassis, possibly the most recognizable drift platform of all time. The SR is a light, compact engine that gives these cars a close to 50/50 weight distribution.
You might be thinking ‘What about all the swaps people put in S-Chassis’. Sure, people love RB, JZ, and even LS motors. All of which have greater power potential, but you lose this beautiful weight distribution of the SR.
Methodical engineering
When it was first conceived, drifting wasn’t a thing. Nevertheless, the engineers cooked up something that could withstand a tremendous amount of abuse.
Unlike its Honda counterparts, the SR is a closed-deck block. This means more rigidity, however. The crankshaft and connecting rods are forged, with turbo engines getting thicker conrods. The pistons are cast, but DET engines have oil squirters to cool them down. Pistons are thought to be a major weak point, but with proper tuning, they can hold up to more power than people think.
Again, the head flows pretty well. Some people might contest this. Sure, when compared with something more contemporary like the K-Series, the SR lags behind. But, during the 90’s it was impressive and it still hangs with modern 4-cylinder to this day.
Aftermarket support & customizability
This platform is kinda like the Build-A-Bear workshop of JDM engines. If you have the budget, the possibilities are endless.
Parts have been developed all over the globe. If you’re a purist, you can build an SR with only OG brands: HKS, Tomei, Apexi, JUN, etc. The boys down unda’ in Australia in New Zealand have built some cool stuff; Kelford Cams and Hypertune come to mind. Right here in the US, Mazworx has developed some pretty gnarly drag SRs.
If you want, you can just do bolt-ons. Or your build can snowball.. pretty much indefinitely. You could build a stroker engine, swap on a VVL head (effectively Nissan’s VTEC), you could add sleeves, maybe even a billet block.
It’s easy to get scope creep when building an SR, but in the next section we’ll explain why simplicity is normally best.
Where the SR does & doesn’t shine
From the early days, drifters in Japan pretty much ‘solved’ the SR - they cooked up the perfect recipe to build one.
The idea isn’t to strap on the biggest turbo and build a dyno queen, but rather, to build a reliable, high-response engine that would give the driver many enjoyable track days with minimal effort. This method has been going strong for the last 30 years.
Simplicity is key. A typical build would leave the internals mostly stock, besides an Apexi head gasket, some upgraded springs, and drop-in cams. Then, it gets a bolt-on turbo, injectors, and a few other odds and ends, plus an Apexi Power FC for tuning. This is good for 300-350HP. Not a ton, but the Japanese philosophy for building cars is centered around driver mod.
In the West, we love overbuilding things. Problems happen when you start to push the SR past 550 WHP. The stock sleeves and transmission won’t like this. And this is where many builds have spiraled out of control.
Sure, you can build it to your heart’s content, but you’re going to get diminishing returns. At this level, it would be pragmatic to switch to a different platform, for example, a JZ or LS. Not to mention: big turbo SRs is are lag monsters.
There’s a reason why everyone started copying the Japanese method for building these engines
Version (red top/ notch top, etc)
So, we’ve established that there are many different versions of the SR. But there were also some updates along the way. They can be identified by their valve cover.
‘Redtop’ SR20DET
This is the first version that was put in an S-Chassis, found in both the Silvia and 180sx from 91-93. As the name implies, it came with a red valve cover. The major drawback is a tiny journal-bearing turbo, putting out a whopping 7 psi of boost.
- 205HP
- T25G turbo @ 7 psi
- S13 Silvia/180sx 91-93
‘Blacktop’ SR20DET
Not to be confused with the Notchtop, which also has a black valve cover. This engine was only found in the 180sx from 94-98. Not much changed from the redtop, meanwhile, the s14 got a much improved engine.
- 205HP
- T25G turbo @ 7 psi
- S13 180sx 94-98
- ‘Newer’
‘Notchtop’ or ‘Slant-top’ SR20DET
By far the most sophisticated SR that came in the S-Chassis. These are easily identified because of their distinct valve cover shape. The rear of the valve cover slopes downward and there's a bulge at the front to accommodate valve timing control (VTC). VTC is generally a good thing - it gives faster spool.
The valve cover also has internal baffling, kinda like a built-in catch can. The intake manifold was redesigned and featured a larger throttle body. Above all, the turbo was upgraded to a T28, journal bearing on the S14, and later ball bearing on the S15.
- 250HP
- T28 turbo
- S14/S15 94-2002
- Improved intake manifold
- Improved valve cover
- VTC
Every great engine needs an Achilles heel
And for the SR, it's in the head design. We just got done telling you the head design is pretty good, but we failed to mention its major flaw: the rocker arms tend to fly off. This is because the SR doesn't have fixed, rod-mounted rocker arms. They are wedged between the cams and valves with nothing else holding them in. This problem was addressed on later, FWD versions of the SR.
At high RPM, SRs tend to ‘spit’ rocker arms. They’re especially sensitive to bouncing rev limiter. And yet, they can hold up to drifting, so.. How? It’s not possible to completely solve the issue, but we can mitigate it.
Ditch the rocker arm stoppers. They’re meant to solve the problem, but they don’t. Name brands still sell them, however, the modern thinking is that they don’t help and can actually cause more damage if the rockers fly off.
Here are some mods that actually help: stiffer springs to prevent valve float, solid lifters, and quality cams. Look into the ‘dual valve guide mod’ for even more assurance.
Find a tuner who has SR experience. Setting a slightly lower rev-limiter and making it ‘soft-cut’ help prevent disaster. DON’T RUN 2-STEP ON AN SR. If your tuner suggests it, find a new tuner.
Building an SR20DET in 2025
So, we know the strengths and weaknesses of the SR. But it’s time to get down to brass tacks. What parts should you be considering for an SR build?
These are some recommendations for a stock-block build, good for up to cerca-400HP.
Turbo
With modern turbochargers, you can make insane power on a small-frame unit. It’s one of those cases where you can have your cake and eat it. Picking a turbo is a good starting point as it dictates the rest of your build
If you want simplicity, T28 ball-bearing turbos are still made by Garrett to this day. You could go with a factory unit, or upgrade to the GT2860RS ‘Disco Potato’. Both bolt onto the stock manifold. The T28 is good for around 300 HP, while the disco potato will support a bit more. These turbos are a bit dated, but still get the job done.
If you just got your tax return and feel like splashing some cash, check out the Garrett G-Series lineup. The G25-550 is the smallest in the lineup and a popular choice for the SR. To put in perspective, this turbo is roughly the same size as the OE T28, but capable of around 200 HP more.
They’re not cheap. Also keep in mind, if you want the most out of them you’ll need a manifold, downpipe, lines, and maybe an external wastegate. But if you want some headroom to build your engine and run E85, they won’t disappoint.
*Update: Garrett just launched the G25-585, the same size as the 550, but with a claimed 10% improvement. If you wanna be the first to test one on an SR, we sell em’, just saying…
As an in-between, you could go for an off-brand turbo. Some people have success with them, others not so much. We’re not going to name any because we don’t want to be responsible if it decides to blow up and ruin your engine. All we’re going to say is ‘Don’t run a Temu turbo'.
Exhaust manifold
If you’re not going with a bolt-on turbo, you need an exhaust manifold with the correct flange, whether that’s T3, V-band, or whatever else. Keeping the spirit of the build, we’re going to recommend a bottom mount setup, as opposed to a top mount setup, which is really meant for big turbos.
If you wanna keep it JDM, the Tomei express manifold uses a T2 flange making it compatible with stock turbos.
Artec manifolds are another option. These are cast stainless steel - not cheap, but cool.
Head & valve train
While a stock bottom end is recommended for most, that doesn't mean the engine should be completely unopened. The head gasket is one of the first failure points. If you’re turning up the boost more than a few PSI, you’ll want a Cometic head gasket, and throw in some ARP head studs while you’re there.
The next thing would be a set of cams. Depending on your car’s use, you could throw in a set of drop-in cams and call it a day. If it will be at high RPM for extended periods, like on a drift car, you’ll want to fully build the head with stiffer springs, valves, and possibly the dual valve guide mod we mentioned earlier.
Fueling
Most of the time, side feed injectors with the stock rail will work fine. Sizing of the injectors depends on a bunch of factors, like fuel type, so we can’t recommend a specific size. Just know, you can go up to 1000cc with bolt-in injectors from Deatschwerks.
If you’re running E85, you might have to convert to a top-feed fuel rail to run larger injectors.
Clutch
If you’re doing an SR swap, a new clutch before the engine is installed is a no-brainer. An Exedy clutch will hold more power than stock, while still being driveable. An ACT Xtreme 6-puck will hold a lot of power, but they’re a B to drive (you better have strong calves). If you have the budget, check out Nismo Coppermix options.
Tuning
This is probably the most important category. You’ll need to figure out an engine management solution.
The cheapest and easiest is a chipped stock ECU with a mail-order tune. Check out RS-Enthalpy for this, it only costs about $400.
Of course, a standalone ECU and dyno tune are better. There are tons of brands, and no, tuning your car with a Gameboy (Apexi Power FC) isn’t relevant in 2025; get a Haltech, Link, or other modern standalone.
Going the standalone route gives you a bunch of possibilities like: electronic boost control, flex-fuel, converting from a MAF to MAP… the list goes on and on…
Other mods & tips
We don’t know what car you’re putting an SR in, maybe it’s an S13, maybe not. These are some other mods you might need that go with the chassis more than the engine:
- Front mount intercooler
- Full exhaust system
- Fuel pump
And finally, here’s our advice on mods you DON’T need (spend your money elsewhere)
- Intake manifold (stock makes more torque in most applications)
- Rocker arm stoppers (They don’t really do anything)
Conclusion
The SR20 is one of those legendary engines, unlike the KA24, which is a truck engine (don’t @ us). As such, it has way more potential due to the abundance of aftermarket parts. Despite this, there are some drawbacks, and we failed to mention the elephant in the room.
SRs are getting super expensive. This is all the more reason to keep your build simple and reliable. There’s no need to overbuild it. Keep the mild, upgrade it with quality parts where needed, take it to a competent tuner, and enjoy your 90’s engine which still competes with the best of em’.